1. Field of the Invention
The present invention relates to devices, materials and processes for the purification of water, and more particularly to a material and process for making the material and to a device for removing heavy metals from water utilizing chelating agents bound to filter bed materials.
2. Description of the Prior Art
Increased attention is being paid to the quality of our drinking water. Studies continue to reveal frightening facts about the decline of water quality, the increase of water-borne diseases, the exponential increase in the amount of toxic chemicals in our water tables and an ever-growing awareness that the chemicals employed in water treatment such as Chlorine and Alum under certain conditions can do more harm than good.
Communities are, at last, addressing the task of keeping our common water supply safe through the construction of sewage treatment facilities, water purification plants, the levying of heavier fines against toxic waste dumpers, etc., but these require years of legislative action and major engineering construction programs. However, of the three types of contaminants--bacterial and viral, toxic chemical, and heavy toxic metals--only the first two are addressed in present home purification methods employing filtration.
There is a need to remove toxic heavy metals from our drinking water because of the severe nature of the health hazards. Of particular concern is lead salts, which can leach from the pipes and solder joints of our home plumbing. Therefore, even though the municipal water supply may be free of these toxic materials, we may still be at risk in our homes.
Generally, three approaches can be taken by people at home. They can trust their water supply, purchase water from outside vendors, and purify their tap water at home. More and more people are leaving the first option and choosing one of the others.
With regard to home water purification, there are three systems currently available:
(1) Carbon Filters; these are designed to remove organics like chlorinated hydrocarbons, pesticides, etc., and sediment if they contain cellulosic or paper prefilters. They make water look, smell and taste better, but do not remove significant amounts of bacteria or hazardous toxic metals. U.S. Pat. Nos. 4,107,047, Turetsky, Aug. 15, 1978; 4,107,046, Corder, Aug. 15, 1978; and 3,561,602, Moltor, Feb. 9, 1971, are illustrative of the use of carbon filters and impregnated carbon filters of the prior art.
(2) Reverse Osmosis Filtration; this process removes most larger molecules and takes care of from less than 50% to more than 99% of contaminants, depending upon the particular system. However, R.O. Filters are generally expensive and can break down when saturated with pollutants.
(3) Distillers; steam distillation is a very effective method for reducing nearly all contamination but it is an expensive unit, requires considerable power with resulting operational costs involved, and can produce limited amounts of water per day.
Two further methods exist for purifying water that have not become generally available for drinking water purification. These methods are the use of ion exchange resins (also known as water softeners) and the use of chelating agents. The use of ion exchange resins in water purification has been described in such U.S. Pat. Nos. as 4,182,676, Casolo, Jan. 8, 1980, and 4,100,065, Etzel, July 11, 1978. In utilizing ion exchange resins, heavy metal ions are removed from the water by replacing such ions with lighter-weight ions such as sodium or potassium.
The use of chelating agents for removal of heavy metal ions from water is described in U.S. Pat. No. 4,500,494, Sher, Feb. 19, 1985 in which chelating agents are encapsulated in microcapsules to remove heavy metal ions. U.S. Pat. No. 4,080,171, Sano, Mar. 21, 1978 describes a method for the analysis of heavy metal ions in water utilizing chelating compounds on filter paper to trap the heavy metal ions together with an analysis of the filter paper to identify the heavy metal ions. U.S. Pat. No. 4,238,328, Bowes, Dec. 9, 1980 describes the use of some types of chelating materials in water purification. U.S. Pat. No. 4,220,726, Warshawsky, Sept. 2, 1980 utilizes some types of metal extraction chemicals in association with certain resins for the recovery of heavy metal ions from liquid. None of these prior art patents, however, appear to teach the application of chelating agents to the purification of drinking water in the materials, process and device described in the instant application.
Chelating agents have been found useful in a number of other applications where metal ions must be extracted, deactivated or removed from fluids, i.e., the use in blood banking to remove calcium from the plasma to convert it to serum, or as a means of wiping up spills of radioactive metallic ions in laboratories. Chelates have also been employed in medicine, in Vivo, to remove toxic metals from over-exposed individuals as in lead or mercury poisoning. Chelates enhance excretion of the metal from the body by reducing the body burden of the tissues and passing the chelate/metal complex harmlessly through the kidney and bladder, or they decrease gastrointestinal absorption by the body by forming non-absorbable, insoluble chelates.